Connecting lakes holds promise for Salinas Valley

Jan. 25, 2013

A view of San Antonio Lake's exposed shoreline during the drought of February 2012. The Interlake Tunnel Project will help restore appropriate water levels by using the excess from neighboring Lake Nacimiento, which fills at a faster rate. / Provided

Written by

The Interlake Tunnel Project is a proposed plan to increase Monterey County's water storage capacity by connecting the Nacimiento Reservoir with nearby Lake San Antonio. The completed project will benefit the region by making it easier to capture and store more water and control seasonal flooding. It will also help stop seawater intrusion into underground aquifers, and promote a healthier environment for recreation and wildlife habitat. / Jay Dunn/The Salinas Californian

Interlake Tunnel Project at a glance

• Will connect Nacimiento and San Antonio reservoirs with a 10,000-foot pipeline tunnel. • Cost estimate: $8.7 million • Benefits: Would conserve more water in the San Antonio reservoir for uses that include aquifer recharging in the Salinas Valley and additional flood control for the Salinas River.

Valuable farmland under flood water along River Road between Salinas and Gonzales in 2011. The Interlake Tunnel Project will help to regulate excess water flowing into the river by adding storage capacity during peak periods of rain. / Conner Jay/The Salinas Californian

More

ADVERTISEMENT

A major water project just now in its infancy holds promise of delivering huge benefits to the Salinas Valley — brightening the region’s flood control, water conservation, recreation and environmental picture.

Agencies in Monterey and San Luis Obispo counties are in the very early stages of scoping out a plan to punch a 10,000-foot-long tunnel between Lake Nacimiento and Lake San Antonio that would take advantage of the latter’s available capacity. The concept is simple. During the rainy months, Nacimiento fills three times as fast as San Antonio, resulting in water being released into the Salinas River as a flood-control measure and tens of thousands of acre feet of water flowing to the ocean, according to the Nacimiento Regional Water Management Advisory Committee (NRWMAC).

Instead of sending the water downstream, the Interlake Tunnel Project would connect Nacimiento and San Antonio, using the latter lake’s available capacity to store more water. In 2011, a healthy rain year, Lake San Antonio peaked at just 80 percent of capacity — leaving twice what was needed to store the extra runoff from Lake Nacimiento, according to NRWMAC.

Or to put it another way, Lake San Antonio has only spilled over one time since the mid-1960s. Nacimiento, on the other hand, regularly fills and can sometimes require the release of large amounts of water into the Salinas River.

Origins in Salinas

The concept of the Interlake Tunnel was first devised by the Salinas-based Monterey County Water Resources Agency in the early 1990s as a component to help stop seawater intrusion into Salinas Valley aquifers. At the time, the agency evaluated more than 30 water projects. The agency moved forward, building the Salinas Valley Water Project. Now, with that project complete, the Interlake Tunnel becomes a viable, practical option, said Robert Johnson, the assistant general manager for the county Water Resources Agency.

Water stored in lakes San Antonio and Nacimiento is used throughout the Salinas River Basin for agricultural, domestic, industrial, commercial, recreational and drinking-water purposes. The water from these two lakes is used downstream for groundwater recharge, abatement of saltwater intrusion, and the promotion of fish habitats.

(Page 2 of 3)

The project has the endorsement of the agency’s Reservoir Operations Committee, the Nacitone watershed committee, and the San Luis Obispo County Department of Public Works.

“The project would allow us to capture and store more water — which would allow us to have more water in our ‘bank,’ ” Johnson said. “If you look at Nacimiento as a checking account, and San Antonio as a savings account, then the tunnel could be considered an electronic transfer.”

Flood control

One of the most controversial water issues facing the Salinas Valley is the growers’ need to clear the Salinas River channel to protect their crops from flooding. The channel clearing has run afoul of the Regional Water Quality Control Board as well as area environmental groups.

Farmers argue that if they are not allowed to clear the channel of debris and vegetation, during storms the water will not be able to move through the channel fast enough to prevent it from topping its banks and taking with it valuable topsoil and/or crops. Because flood water can also pick up everything from oil and other toxins to a myriad of pathogens en route to fields of row crops, the fields that experience flooding must remain fallow for a period of time before a new planting can happen, costing growers even more money.

Environmentalists counter that clearing the channel destroys critical wildlife habitat and produces too much silt that eventually flows into Monterey Bay. Farmers, they argue, are planting crops on historic flood plains and should consequently assume the risk of crop losses.

The Monterey County Water Resources Agency is tasked with preparing an environmental study of the channel clearing process, a draft of which is due out in the very near future.

But a saving grace of the Tunnel Project, in theory anyway, is that instead of releasing potentially large volumes of water into the Salinas River, the water could instead be siphoned off to Lake San Antonio, minimizing flood control releases from Nacimiento.

Water conservation

The northern end of the Salinas Valley, as well as the $4.8 billion agricultural economy, are threatened by saltwater intrusion. When groundwater levels in the critical 180-Foot Aquifer and 400-Foot Aquifer are drawn down as a result of extractions being greater than recharge, they become susceptible to seawater seeping in — which is a lose-lose situation for everyone.

(Page 3 of 3)

One of the benefits of the Salinas Valley Water Project is maintaining flow in the Salinas River during the summer months, when pumping in the Salinas Valley is at its greatest. The flows percolate into the groundwater basin, providing recharge, and are diverted to the seawater-intruded area for use on crops, thus stopping pumping in that area, which helps stop seawater intrusion from advancing.

An additional benefit is simply that more water stored in the reservoirs equals more water supply for the valley and its water needs.

Drilling into the funding

Engineering and tunneling don’t come cheap. Susan Robinson, the plan coordinator for the Greater Monterey County Integrated Regional Water Management Plan (IRWMP), has calculated a rough cost estimate at $8.6 million for the tunnel. But the latest round of state grant funding comes up shy of that total.

When voters passed Proposition 84 in 2006, $5.4 billion was allocated statewide for improvements to water quality and supply, flood control, and river and coastal protection. Of that amount, $1 billion was set aside for grants to support water resource and water-related environmental projects as part of the state’s “Integrated Regional Water Management (IRWM) Program.” There are 11 IRWM “funding areas” in the state, including the Central Coast Funding Area, which is comprised of six individual IRWM Regions formed on the basis of geographic factors such as watersheds.

Originally a Salinas Valley IRWM Region was formed, though there were large portions of Monterey County that were not included in any IRWM Plan, which meant that any project located within those areas would not be eligible for IRWM grant funds, Robinson explained. So the Salinas Valley IRWM Region was expanded into the Greater Monterey County IRWM Region, and a new IRWM Plan was developed.

The state has allocated a certain amount of grant funds to each funding area. A total of $52 million has been allocated to the Central Coast funding area for implementation projects. These funds are being made available to the funding areas in three rounds. Round 1 occurred in 2011. About $7.6 million is available now in Round 2 for the Central Coast funding area. Each of the six IRWM Regions in the Central Coast funding area can submit an application to the state for some or all of those funds to support water-related implementation projects within their regions. It’s a competitive process. The state will decide who receives the grant funds.

The money is released in rounds, the first released several years ago, and the second is in the process of accepting grant applications. The third and final tranche will be released in a few years. Five of the six regions are applying; some are applying for the full amount but others are applying for less.

Robinson describes the process as “competitive but cooperative.”

While the Interlake Tunnel is high on the Monterey County IRWM Region’s priority list (No. 3), the cost of the project, at $8.6 million, exceeds the total IRWM grant funds available in Round 2.

There are, of course, additional sources of funding, perhaps through other grants that Robinson said she will be researching. Ultimately it is a project that is within reach that holds the potential of resolving several of the most serious water challenges the county faces.